1. Field of the Invention
The present invention relates to fuel injection control devices for internal combustion engines. In particular, the present invention relates to a fuel injection control device for controlling injection of fuel into an internal combustion engine immediately after the engine has started.
2. Description of the Related Art
FIG. 4 is a graph showing a ratio A/F of the volume of air to fuel, revolution Ne, and the amount of injected fuel, when starting an internal combustion engine. Hitherto, a very large amount of fuel has been injected during a starting mode (between times t1 and t2), that is, after the engine is driven to start by a starter motor until the engine is brought into a full combustion state at a revolution of, for example, 500 rpm. Thereafter,-at the beginning of a normal operation mode before a stable operation starts at a time t3, the fuel to be injected has been reduced gradually so as not to hinder stable combustion (the amount of injected fuel is shown by dotted lines A in FIG. 4), and the ratio A/F of the volume of air to fuel has been controlled so as to be nearest to 14. 7 which is the theoretical air to fuel ratio.
During the starting mode (times t1 to t2), a very large amount of fuel is injected. In the starting mode, a phenomenon in which fuel gathers and adheres to the inside adjacent to an injector I of an intake pipe, as shown in FIG. 15, is likely to occur because the temperature of the internal combustion engine has not yet been sufficiently increased, the pressure in the intake pipe is increased, and the volume of air passing through the intake pipe has not been increased; therefore it is difficult for the fuel to vaporize.
In the normal operation mode (after the time t2), the fuel adhering to the intake pipe is likely to evaporate and to be led into a cylinder because of the increased air passing through the intake pipe and the reduced pressure therein. Particularly at the beginning (times t2 to t3) of the normal operation mode, that is, immediately after the starting mode, in most cases, the fuel fed into the cylinder is increased by that which has adhered to the intake pipe. In the normal operation mode immediately after the starting mode (times t2 to t3), relatively a large amount of the fuel is injected so as to stabilize the combustion, in which the fuel which has adhered to the intake pipe must be considered in addition to the fuel to be injected by the injector I. However, it is difficult to control the amount of fuel during this period, which is a rapid transition phase. Therefore, the amount of the fuel adhered to the intake pipe has been hitherto corrected in a stable operation mode (after the time t3) of the internal combustion engine.
In the above-described known fuel injection control device, a relatively large amount of fuel is injected in the normal operation immediately after the starting mode so as to stabilize the combustion, rather than reducing the fuel so as to correct for the amount of fuel for injection by an amount of fuel adhered to the inside of the intake pipe. As a result, the ratio A/F in this mode is greatly biased toward an excessive fuel-supply side, as shown by the dotted lines A in FIG. 4, whereby combustion exhaust gas is increased, thereby causing a problem with the emission control standards which have been recently difficult to meet.
Accordingly, it is an object of the present invention to provide a fuel injection control device for an internal combustion engine, in which the amount of combustion exhaust gas immediately after the engine is brought into a complete combustion state is reduced by considering the amount of fuel adhered to the inside of an intake pipe when starting the engine, that is, by reducing the amount of fuel to be injected.
To these ends, according to an aspect of the present invention, a fuel injection control device for an internal combustion engine comprises a revolution detecting unit for detecting revolution of the internal combustion engine; an injector-for injecting fuel into the internal combustion engine; and a fuel injection control unit for controlling the injection of fuel of the injector. The fuel injection control unit includes an engine-start-completion detecting unit for detecting whether or not the internal combustion engine has started, and a fuel-injection-amount correcting unit for correcting the amount of fuel to be injected, after the engine has started, by an amount of fuel for correction obtained by considering the amount of fuel remaining uncombusted when starting the engine and in accordance with one of the number of times of fuel injection, revolution of the internal combustion engine, and the elapse of time.
The fuel injection control device for an internal combustion engine according to the present invention may further comprise at least one of a load determining unit for determining the load on the internal combustion engine and an engine-temperature determining unit for determining the temperature of the internal combustion engine. In the fuel-injection-amount correcting unit, the amount of fuel for correction is adjusted in accordance with at least one of the load on the internal combustion engine and the temperature thereof.
In the fuel injection control device for an internal combustion engine according to the present invention, the fuel injection control unit injects fuel a plurality of times every cycle of the internal combustion engine, and the fuel-injection-amount correcting unit-corrects the amount of fuel to be injected by an amount of fuel for correction determined for each of the plurality of times of injection.
The fuel injection control device for an internal combustion engine according to the present invention may further comprise a fuel-characteristic determining unit for determining the characteristics of the fuel by detecting the elapse of time from the start of cranking until first combustion. The fuel-injection-amount correcting unit corrects the amount of fuel to be injected by an amount of fuel for correction adjusted in accordance with the determination of the fuel-characteristic determining unit.